Air India 171 – Engine Shutdown Mystery Part 2

CCTV footage also showed that immediately after liftoff, the Ram Air Turbine (RAT) deployed.

The RAT is an emergency power source that automatically deploys when engine power is lost.

It provides electricity to essential aircraft systems during emergencies.

The deployment of the RAT was a clear indication that something highly unusual had occurred.

The footage also showed the aircraft rapidly losing altitude.

This was confirmed by flight recorder data, which indicated that the N2 values of both engines had fallen below their minimum idle speed.

At 1:39 PM and 5 seconds, ATC recordings captured a MAYDAY distress call.

When air traffic control requested the aircraft's callsign, no further response was received.

ATC personnel then observed the aircraft crash outside the airport boundary and immediately activated emergency response procedures.

The aircraft, flying straight ahead from Runway 23, first struck a chimney belonging to an Army Medical Corps building approximately 1,600 meters from the runway.

It then collided with the BJ Medical College hostel.

The wreckage was scattered across an area approximately 1,000 feet long and 400 feet wide.

In this accident, 12 crew members and 229 passengers lost their lives.

Additionally, 19 people on the ground were also killed.

Only one passenger survived, reportedly because he was seated near an emergency exit and managed to escape.

The preliminary investigation report spans 15 pages and provides detailed information about the accident.

Investigators recovered the flap handle assembly from the wreckage.

It was found in the 5-degree flap position, which is a normal takeoff configuration.

This finding was also confirmed by flight recorder data.

The landing gear lever was found in the DOWN position.

Although the thrust levers were badly damaged by fire, evidence indicated that they remained in the forward position until impact.

The most important discovery involved the fuel control switches.

Investigators found both switches in the RUN position.

This means the pilots had turned the switches back on before the crash.

Normally, these fuel switches are designed so that only a human can operate them.

Each switch is protected by a locking mechanism.

The purpose of this lock is to prevent accidental activation or deactivation.

To move a fuel switch, a pilot typically needs both hands.

One hand presses the lock release while the other moves the switch.

This is what makes the situation so puzzling.

According to the design, it is extremely difficult to accidentally move a fuel switch using only one hand.

So if the pilots did not intentionally turn off the switches—as suggested by the cockpit voice recording—then who did?

And if it happened accidentally, how could both switches have been turned off one after another?

The investigation report also notes that both fuel switches moved to the cutoff position only one second apart.

This timing appears consistent with deliberate human action.

Later, both switches were turned back on.

However, by then it was already too late.

According to investigators, approximately 10 seconds passed between fuel cutoff and fuel restoration for Engine 1.

For Engine 2, the interval was approximately 14 seconds.

Evidence also suggests that both engines had begun recovering and were starting to produce thrust again.

Unfortunately, the aircraft crashed before sufficient power could be restored.

This is where the biggest mystery begins.

Up until takeoff, Flight AI171 had been operating perfectly.

Everything—from the engines to the fuel loaded onto the aircraft—appeared normal.

Investigators even collected fuel samples from the tanker that refueled AI171 and sent them to a laboratory for testing.

No abnormalities were found.

If everything was functioning normally, then why were the fuel switches turned off?

Were they intentionally moved?

Or was there a failure in the locking mechanism?

The report mentions another important detail.

In 2018, the Federal Aviation Administration (FAA) issued a Special Airworthiness Information Bulletin (SAIB).

The bulletin warned operators about the possibility of issues involving fuel control switch locking mechanisms.

In other words, concerns about the reliability of these locks had already existed within the aviation industry.

The bulletin was issued after complaints from operators of certain Boeing 737 aircraft.

This means that similar issues had previously been reported on some Boeing airplanes.

The fuel control switch design, including the locking feature, is similar across multiple Boeing aircraft models.

One of the relevant components carries the part number 4TL837-3D.

The same part was installed on Air India Flight AI171's aircraft, VT-ANB.

The FAA had warned seven years earlier that some fuel control switches could be installed with the lock disengaged.

Air India did not carry out the recommended inspection because it was advisory rather than mandatory.

However, even if we assume that the locking mechanism was defective and the switches somehow moved accidentally during takeoff, another question remains:

How could both switches have moved to the cutoff position one after another, separated by only one second?

That level of coincidence seems difficult to explain.

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